Three canister regenerative co2 system



Dec. 5, 1967 W. E. ARNOLDI 3,355,860

THREE CNISTER REGENERATIVE CO2 SYSTEM Filed Feb. 18, 1965 2 Sheets-Sheet1.

INVENTOR ZOWQ WALTER E- ARNOLDI 6` i BY d?. /M//w C//V //Q ATTORNEY Dec.5, 1967 w. E. ARNOLDI THREE CANISTER REGENERATIVE CO2 SYSTEM 2Sheets-Sheet 2 Filed Feb, 18, 1965 FIC--3 W ai I C mi :J7 @a ha f/IIL Z*I5* ,C wHzz 5 5H U f im A v a www. @MQW @Wi 33H a fn n 7%/ f il Ii ili5 w c @2f d@ w m .1W N 7, u w mw 4 Umd a RM a/a M,

United States Patent O THREE CANISTER REGENERATHVE C02 SYSTEM Walter E.Arnoldi, West Hartford, Conn., assigner to United Aircraft Corporation,East Hartford, Conn., a corporation of Delaware Filed Feb. 18, 1965,Ser. No. 433,633

6 Claims. (Cl. 55-31) This invention relates to air purification systemsand more particularly to carbon dioxide removal systems of theadsorption type for removal of carbon dioxide from sealed compartmentssubject to carbon dioxide contamination due to exhalation of humanoccupants.

The system of this invention is useful in controlling the carbon dioxidelevel in airplane cabins and other closed compartments having humanoccupants, but was developed specifically for controlling the carbondioxide level in manned space ships which may undertake protractedmissions.

It is therefore an object of this invention to provide an improvedsystem of the type described capable of maintaining the carbon -dioxidelevel in a closed compartment at a tolerable level over long periods oftime.

It is lanother object of this invention to provide such a system whichis relatively simple, extremely reliable in operation and which iscapable of operation over long periods of time.

l More specifically the present invention provides three canisterscontaining an artificial zeolite, sometimes referred to as molecularsieves, or microtraps, e-ach having two outlets and two inlets. Eachoutlet and each inlet is controlled by a normally closed valve. Thesevalves may be operated by rotary actuators or they may be of thesolenoid operated type and are governed by a suitable electriccontroller to provide the desired cycling of the valves.

The cycle is carried out in three stages during which the moist CO2contaminated air from the space ship compartment is introducedsuccessively into the three canisters wherein H2O and CO2 are adsorbedfrom the air. At the same time that adsorption of H2O and CO2 is takingplace in one canister, desorption of CO2 is taking place in anothercanister and desorption of' H2O is taking place in still anothercanister and the CO2 free air with its moisture restored is beingreturned to the compartment.

It is a further object of this invention to provide a system as abovedescribed for the removal of CO2 for a closed compartment.

Other objects of this invention are to use the eluent air from the H2Oand CO2 adsorbing canister to accomplish the desorption of H2O from thesecond canister; and to cycle the heat from the lirst canister throughthe second and third canisters and back to the rst canister, so thatonce-the system 4has been put into operation only enough heat will needto be added to make up for the normal he'at losses in the system.

These and other objects and advantages of the system will be evident orwill be pointed out in connection with the following detaileddescription of a preferred embodiment of the invention shown in theaccompanying drawings.

In these drawings:

FIG. 1 shows schematically the improved CO2 removal system of thisinvention, the valves being shown in the first of three stages of thecycle;

FIG. 2 shows the same system with the Valves in the positions theyoccupy in the second stage ofthe cycle; and

FIG. 3 shows the same system with the valves in the positions theyoccupy in the third and last stage of the cycle.

g@ Patented Dec. 5, 1957 ICC Referring to FIG. l, three identicalcanisters A, B and C are provided which contain artificial zeolite,capable of absorbing large quantities of H2O and CO2. Since the threemolecular sieve canisters A, B and C are identical and have identicalvalving, only canister A and its valves will be described in detail.

On its first, or inlet, end, which is the left-hand end in FIG. 1,canister A has an inlet -duct 10A connected with a duct 12 from a blower14 that supplies all the canisters with cabin air from the space ship.This end of canister A also has an outlet duct 16A that is connectedwith a duct 1S by which air is returned to the cabin. Duct 10A has in ita two-position valve 26A which may be a normally closed solenoid valve.In duct 16A a similar twoposition valve 22A is provided. On its second,or righthand, end, canister A has a duct 24A that is connected to a duct26 which is common to all the canisters. Duct 24A has a two-positionvalve 28A. Canister A also has on its right-hand end a duct 36A which isconnected to a vacuum duct 32. This latter duct may, in the case of aspace ship, be simply discharged into space. Duct 30A is provided with avalve 34A which, like all the valves in FIG. l, is a two-position,closed or open valve.

Canister A is also provided with a heating element 36a for heating airentering the canister through duct 24A from duct 26 (FIG. 3). Heatingelement 36a receives its power from a battery 38 and is controlled by aswitch 40a, here shown diagrammatically as a manually operated switch.It will be understood that the valves and the heater switches of FIG. lare automatically operated in the proper sequence and for the propertime to correctly cycle the heat supplied to the canisters by theheaters and open the valves, as hereinafter described. This may be doneby any one of a number of well-known mechanisms. For example, a drumcontroller can be used having peripheral arcuate contact strips whichare engaged by brushes as the drum rotates through one revolution toenergize and open the normally closed valves in the proper sequence andfor the proper time and to energize the heater elements as required.

Canisters B and C yare identical in features described for canister Aabove and have identical valve controlled connections with ducts 12, 18,26 and 32. Their connecting ducts and valves are accordingly numbered bythe same convention except that they also bear individual letterdesignations. FIGS. 2 and 3 are identical with FIG. 1 except for thepositions of the various valves and, for simplication, the omission ofthe heater circuits.

In the tirst stage of the cycle shown in FIG. 1, canister A is theadsorbing canister and valves 20A, 28A,. 28B, 22B and 34C are energized,as shown, to open them. All other valves remain closed. Contaminated airfrom the cabin is led through the system under pressure from the blower14, rst entering duct 12. Since valve 20A is open, CO2 contaminated airenters canister A through duct 10A and valve 20A and slowly passesthrough the crystalline zeolite bed of the canister where it loses itsH2O and CO2 content by adsorption and passes out through duct 24A toduct 26. The air from canister A, heated by residual heat in canister Afrom a previous cycle and also by heat into adsorption of CO2, passesthrough duct 26 and valve 28B into canister B. Upon entering canister B,the air is further heated to a temperature necessary for desorption ofmoisture from cani-ster B by heater Sb, which is energized by theclosing of its switch 4Gb. The air as it passes through the bed ofcanister B picks up H2O and then passes through duct 16B and open valve22B to duct 18 by which it is returned to the.

cabin with its normal moisture content intact. The path of the air abovedescribed is indicated in FIG. l by full line arrows.

During the time that H2O and CO2 are being adsorbed in canister A andAH2O is being desorbed in canister B, canister C is connected by ductSiiC and open valve 34C to duct 32 which leads to an evacuatedcontainer. Thus while the PIG. l stage of the cycle is in progress, CO2lett in canister C by a previous cycle is exhausted and discharged asindicated by the broken line arrows.

FIG. 2 shows the second stage of the cycle. Here valves 2GB, 22C, 34A,23B and 28C are open and air from blower 12, as indicated by the fullline arrows, liows through ducts 12 and MB and valve 26B to canisterAfter passing through the canister, in which its H20 and CO2 content isadsorbed, it leaves through duct 24B and valve 28B. It should be notedhere than canister B was previously heated during stage l by the hot airwhich was heated by residual heat from canister A and by heater 36h.rthis heat in canister B is removed by the cabin air entering canister Band is carried into canister C. Heater element 36C will be energized toheat the air entering canister C, thereby replacing any heat lost in thefirst stage of the cycle. As the air moves through the zeolite bed ofthe canister C it desorbs H2O and returns to the cabin through duct 16C,open valve 22C and duct 1% with its normal H2O content and free fromCO2. Simultaneously with this stage or" the cycle just described valve34A is open to allow CO2 in canister A to be exhausted through ducts 39Aand 32.

In the iinal stage of the cycle illustrated in FIG. 3, valves 26C, 28C,28A, 22A and 34B are open. This permits cabin air from blower 14y toflow through ducts l2. and 16C, and valve 20C into canister C where H2Oand CO2 are adsorbed. The air leaves by duct 24C, valve 2SC, duct 26,valve 28A and duct 24A leading to canister A where H2O left by stage 1,FG. l, of the cycle is desorbed from the zeolite bed. The air enteringcanister A is heated by energizing heater 36a. The moist air then leavescanister A and returns to the cabin through duct 16A, valve 22A and duct18.

Canister B is connected to vacuum through duct 30B, valve 34B and duct32 through which its CO2 content is exhausted. This completes one fuilcycle of operation which is repeated indefinitely as long as the shipremains in space. It should be noted here that the adsorbing, desorbingand evacuating times are the same. This time is determined by the lengthof time it takes the heat front to pass through the length of theZeolite bed.

From the above description of a full cycle of the system it will beevident that an automatic cle-contamination system has been providedwhich requires fewer canisters than previous systems. It will also beevident that the system is simple and reliable in operation.

An outstanding feature of this invention will be evident fromconsidering, for example, stage three of the above described cycle.Since air entering canister C from the cabin is heated during adsorptionin canister C, in the process of cooling a previously -hot bed in thiscanister, this heat contributes to the requirement for desorbing H2Ofrom canister A into which the etiiuent from canister Cl flows, thusperforming a partial conservation of heat. As a result, no additionalheat exchangers are required for conservation ot heat.

A yfurther outstanding feature of the system of this in vention is itsconservation of H2O which is returned to the cabin with thedecontaminated air. Also, since the adsorbing time equals the desorbingtime, the heat can be cycled from canister A to canister B to canister Cto canister A with a minimum energy input.

While only one embodiment of the invention has been shown and described,it will be evident that various changes may be made in the constructionand arrangement of the parts without exceeding the scope of theinvention as dened by the following claims.

I claim:

1. Apparatus for removing CO2 from cabin air comprising threemolecular-sieve canisters, each having an air inlet connection on theiirst end of each canister, a first outlet connection on the first endof each canister, a second outlet connection on the second end of eachcanister, and a fourth intercanister connection on the second end ofeach cansiter, a twoposition `open or closed valve in each of saidconnections, means for supplying cabin air to all of said inietconnections, duct means for connecting all of said iirst outletconnections to the cabin, duct means for connecting all of said secondoutiet connections to vacuum, and duct. means common to all three ofsaid canisters for connecting said fourth intercanister connections.

2. Apparatus for removing CO2 from a sealed compartment subject to CO2contamination due to exhalation of a human occupant comprising threemolecular-sieve canisters, means including a blower for exhaustingcontaminated air from the compartment, and means for selectively linkingany two of said three canisters in series between the outlet of saidblower and said compartment including duct connections from the iirstend of each canister to the outlet of said blower, duct connections fromthe iirst end of each canister to the compartment, duct connections fromthe second end of each canister to vacuum, a duct common to all threecanisters having a canister linking duct connection to the second end ofeach of said canisters, and a two-position normally closed valve in eachof said duct connections.

3. The three stage method of operating a three canister regenerative COQsystem for cabin air purification which includes in the rst stage thesteps of circuiating H2O and CO2 laden air from the cabin through thefirst ot the three canisters to adsorb the H2O and CO2 content of theair, returning the air from the iirst canister through the secondcanister to desorb the H2O content of said second canister, returningthe moist air from said second canister to the cabin, and simultaneouslyconnecting the third rcanister to vacuum; in the second stagecirculating -izO and CO2 laden air from the cabin through the secondcanister to adsorb the H2O and CO2 content of the air, returning the airto the cabin through the third canister to adsorb the H2O content ofsaid third canister, and simultaneously connecting the iirst canister tovacuum to exhaust its CO2 content; and in the third stage circulatingthe H2O and CO2 laden air from the cabin through the third canister toadsorb the H2O and CO2 content of the air, passing the air from thethird canister through the iirst canister to desorb the H2O content ofthe first canister, returning the moist air from the first canister tothecabin, and simultaneously connecting the second canister to vacuum toexhaust the CO2 content of the second canister.

4. The steps of removing CO2 from cabin air by a threestage method usingthree canisters of the type containing regenerable solid adsorbent,which consists in the iirst stage in simultaneously supplying cabin airto one of the canisters for adsorption of H2O and CO2, discharging theair from said one canister into a second canister for desorption of theH20 in that canister, discharging the air from the second canister withits moisture content back to the: cabin, and connecting a third canisterto vacuum to discharge CO2 therefrom; in the second stage simultaneouslysupplying air from the cabin to the second canister for adsorption ofH2O and CO2, discharging the air from said second canister into thethird canister to desorb H2O, discharging the air from the thirdcanister with its moisture content to the cabin, and connecting thefirst canister to vacuum to exhaust its CO2 content; and in the thirdstage admitting air from the cabin to thethird canister for adsorptionof H2O and CO2, discharging the air from the third canister through theiirst canister to desorb H20 and thence with its moisture content backto the cabin, and connecting the second canister to vacuum to exhaustits CO2 content; and repeating the cycle through `these three stagescontinuously.

5. The method of claim 4 in which in the first stage of the cycle heatis supplied to the air as needed as it enters said second canister, andheat is `supplied in the second and third stages of the cycle to the airas it enters said third and rst canisters respectively.

6. The three-stage method of operating a three-canister regenerative CO2system for cabin air puriication in which the canisters contain aregenerable solid adsorbent of artificial zeolite, which includes in theiirst stage the steps of circulating H2O and CO2 laden air from thecabin through the first of the three canisters to adsorb the H2O and CO2content of the air in the canister, returning the heated air from thefirst canister through the second canister to the cabin, heat beingadded to the air as it enters the second canister, to desorb H2O in saidsecond canister, and simultaneously connecting the third canister tovacuum to exhaust any CO2 therein; in the second stage circulating H2Oand CO2 laden air from the cabin through the second canister to adsorbH2O and CO2 in the air, returning the air from the second canister tothe cabin through the third canister to desorb H2O in said thirdcanister, heat being added to the air entering the third canister ifneeded to replace the heat lost in the system, and simultaneouslyconnecting the tirst canister to vacuum to exhaust its CO2 content; andin the third stage circulating H2O and CO2 laden air from the cabinthrough the third canister to adsorb the H2O and CO2 content, passingthe `air issuing from the third canister through said first canister todesor-b H2O in the latter, heat being added to the air entering thefirst .canister to replace heat lost in the system, returning the moistair from the iirst canister to the cabin, and simultaneously connectingsaid second canister to vacuum to exhaust the CO2 content of the latter;and repeating the three-stage cycle continuously.

References Cited UNITED STATES PATENTS 3,130,021 4/1964 Milton 55-623,150,942 9/1964 Vasan 55-31 3,164,454 1/ 1965 Wilson 55-68 3,206,918 9/1965 Robinson 55-179 3,221,477 12/1965 Arnoldi et al. 55-75 REUBENFRIEDMAN, Primary Examiner, SAMIH N. ZAHARNA, Examiner. C. N. HART,Assistant Examiner.

3. THE THREE STAGE METHOD OF OPERATING A THREE CANISTER REGENERATIVE CO2SYSTEM FOR CABIN AIR PURIFICATION WHICH INCLUDES IN THE FIRST STAGE THESTEPS OF CIRCULATING H2O AND CO2 LADEN AIR FROM THE CABIN THROUGH THEFIRST OF THE THREE CANISTERS TO ADSORB THE H2O AND CO2 CONTENT OF THEAIR, RETURNING THE AIR FROM THE FIRST CANISTER THROUGH THE SECONDCANISTER TO DESORB THE H2O CONTENT OF SAID SECOND CANISTER, RETURNINGTHE MOIST AIR FROM SAID SECOND CANISTER TO THE CABIN, AND SIMULTANEOUSLYCONNECTING THE THIRD CANISTER TO VACUUM; IN THE SECOND STAGE CIRCULATINGH2O AND CO2 LADEN AIR FROM THE CABIN THROUGH THE SECOND CANISTER TOADSORB THE H2O AND CO2 CONTENT OF THE AIR, RETURNING THE AIR TO THECABIN THROUGH THE THIRD CANISTER TO ADSORB THE H2O CONTENT OF SAID THIRDCANISTER, AND SIMULTANEOUSLY CONNECTING THE FIRST CANISTER TO VACUUM TOEXHAUST ITS CO2 CONTENT; AND IN THE THIRD STAGE CIRCULATING THE H2O ANDCO2 LADEN AIR FROM THE CABIN THROUGH THE THIRD CANISTER TO ADSORB THEH2O AND CO2 CONTENT OF THE AIR, PASSING THE AIR FROM THE THIRD CANISTERTHROUGH THE FIRST CANISTER TO DESORB THE H2O CONTENT OF THE FIRSTCANISTER, RETURNING THE MOIST AIR FROM THE FIRST CANISTER TO THE CABIN,AND SIMULTANEOUSLY CONNECTING THE SECOND CANISTER TO VACUUM TO EXHAUSTTHE CO2 CONTENT OF THE SECOND CANISTER.